Natural environmental radioactivity and estimation of radiation exposure from saline soils

The study was conducted for the investigation of amount of radioactivity in the barren and cultivated soil of Bio saline Research Station in Pakka Anna, established by Nuclear Institute for Agriculture and Biology (NIAB) in 1990, 34 km. away from the city of Faisalabad, in the Punjab province of Pakistan. The studies were done on an area of about 100 hectares of two types of virgin and fertilized saline soils. The technique of gamma ray spectrometry was applied using HPGe (high purity germanium) gamma ray detector and a PC based MCA. Activity concentration levels due to ⁴⁰K, ¹³⁷Cs, ²²⁶Ra and ²³²Th were measured in 250 saline soil samples collected at a spacing of about 4 hectares at the depth level of 0–25 cm. with a step of 5 cm. depth. Activity concentrations ranges of the concerned radionuclides for both of the soils were as follows: ⁴⁰K, for virgin and cultivated saline soil was 500–610.2 and Bq/kg 560.2–635.6 respectively; ¹³⁷Cs, 3.57–3.63 and 1.98–5.15 Bq/kg ²³⁸U, 26.3–31.6 and 30.3–38.7 Bq/kg, and ²³²Th, 50.6–55.3 and 50.6–64.0 Bq/kg respectively. The absorbed dose rate in air lies in the region 63–73 nGyh^-1 and 68–83 nGyh^-1 for virgin and fertilized soils respectively. This indicates that this region lies in the area of higher radiation background, while comparing with the worlds’ average. The slightly higher value of dose in the fertilized farm may be due to the use of fertilizers for cultivation. Before the radiometric measurements, chemical analysis for concentration of Na, Ca and Mg was also carried out along with the measurement of electrical conductivity and pH of the soil samples.     

Natural radioactivity measurements in beach sand along southern coast of Orissa,eastern India

The beach placer deposits in the southern coastal Orissa, India may have significant levels of radiation due to the presence of Th and U bearing minerals such as monazite and zircon. In this study, Gopalpur and Rushikulya beach regions were selected to study the ambient radiation environment. The average activity concentrations of radioactive elements such as ²³²Th, ²³⁸U and ⁴⁰K of beach sand samples were measured by γ-ray spectrometry using a HPGe detector, and found to be much higher than the internationally accepted values. The cross plots of eTh/eU and eTh/K inferred that the sand samples of Gopalpur and Rushikulya beach placer deposit were deposited in leached uranium and an oxidising environment. The absorbed γ dose rate levels of the study areas are similar to other monazite sand-bearing HBRAs of southern and southwestern coastal regions of India and of world. Different radiation hazard indices were estimated for the present study area and were found to be much higher than the internationally accepted values. Hence, Gopalpur and Rushikulya beach placer region can be considered as a high background radiation area and a potential zone for radiogenic heavy mineral exploration.     

Investigation of calcareous beach sands in the Akumal and Tulum areas for use in constructed wetlands,Eastern Yucatan Peninsula

Constructed wetlands can be a low-cost, ecologically based technology to locally treat domestic wastewater prior to discharge. Wetland systems implemented in the resort village of Akumal in the state of Quintana Roo, in the Yucatan Peninsula of Mexico have been considered moderately successful over approximately 10 years of operation. Yet the wide-scale implementation of constructed wetlands has not occurred in the region nor throughout Mexico due largely to the cost of the crushed aggregate used in these systems. Variation in the geotechnical and mineralogical properties of 29 samples of local calcareous beach sands collected from the tourist areas of Akumal and Tulum in the Yucatan, Mexico were analyzed and compared to those of crushed aggregate currently used in constructed wetland systems in Akumal. Powder X-ray diffraction on beach sand samples from Akumal and Tulum indicates that the proportion of aragonite varies from 24 to 84%, calcite varies from 7 to 38% and Mg-calcite varied from 8 to 57% compared to crushed aggregate which consists of 0–25% aragonite and 75–100% calcite. Compared to crushed aggregate beach sands are unimodal and have better uniformity coefficients, making them a better geotechnical choice than crushed sands with respect to these properties. Grain-size of the beach sands is much smaller compared to that of the crushed aggregate currently used in the constructed wetland systems in Akumal which should enhance the efficiency of the filtration of organic matter and bacteria. The average hydraulic conductivity measurements of 0.010 and 0.016 cm/s for beach sands from Akumal and Tulum, respectively are comparable or less than the average of 0.016 cm/s for crushed aggregate currently used in engineered wetland systems. Yet a combination of high bulk porosity, intragranular pores, and the presence of Mg-calcite observed in beach sands may likely result in higher dissolution rates versus the crushed aggregate. Preliminary assessment suggests that the use of local sand may be a technical, economic, and perceptual enhancement to the systems. Still a careful and thorough analysis of the potential environmental and aesthetic impacts of mining beach sands is necessary.     

Variations of some heavy minerals in recent beach sands

The influence of shape, size, and specific gravity of mineral grains on the variation of the content of these minerals in beach sands has been investigated for fixed conditions of sedimentation on the beaches of the Baltic Sea and Michigan Lake. The coefficient of variation was used as a measure of the variance. Linear models tested by the analysis of variance were applied and revealed that the shape of grains and the combined effect of the size and specific gravity are responsible for the main part of the variation.     

Natural radioactivity distribution studies in Trivandrum district,Kerala, India

The distribution pattern of radioactive minerals in Trivandrum district of Kerala has been investigated. The surface radioactivity was measured employing a jeep-mounted four-channel gamma-ray spectrometer coupled to a high volume Na I (T1) crystal detector. The distribution of radioactivity has been correlated with the corresponding litho-units and major structures of the study area. The total countrate from sedimentaries including beach sands and pegmatite rich zones (～ 3,500 CPS) are significantly higher than that of the laterites and gneisses which are substantiated by laboratory studies.     

The study of relative density in some dune and beach sands

A new method was developed for the measurement of relative density in natural sand deposits. The method is based on hardening sand in the field, so that undisturbed samples can be obtained, and the later removal of the organic hardener in the laboratory. In the study of two coastal dunes use was made of “peels” which reveal in detail the internal structure of the sand. A definite relationship was established between relative density of the dune sand, its internal structure and mode of deposition. Very high relative densities, approaching and even exceeding 100%, were found in sand deposited by accretion on the top of the dunes. Low to very low relative densities were measured in slip deposits formed by avalanching of sand on the leeward slope of the dunes. High densities in accretion deposits are attributed to sand movement by saltation taking place during the accumulation of the sand and the very high kinetic energies expended during this transportation process. Low densities in the slip deposits are attributed to the process of avalanching which involves minimum energy expenditure. A more or less constant relative density of around 80% was found in the stretch of beach sand studied.     

Methane-derived carbonate cements in barrier and beach sands of a subtropical delta complex

Highly negative δC¹³ values, ?18 to ? 40%., for carbonate cements found in Recent barrier and beach sands of the Mississippi River Delta complex strongly suggest that considerable carbon is furnished to the CaCO₃ cements by either chemical or biological oxidation of CH₄. These cemented sands are commonly found on beaches of the Chandeleur barrier island chain and other sites along the Louisiana coast where Holocene sands are rapidly transgressing over highly organic marsh deposits. Generation of CH₄ from underlying anoxic marsh sediments, followed by vertical migration and oxidation to CO₂ in the porous overlying sand, appears to be the unique set of conditions regulating this process of carbonate cementation.     

Distribution and properties of placer ilmenite in East Rosetta beach sands,Egypt

This work deals with a concise but comprehensive study of Ilmenite distribution in the beach sands of east Rosetta. This area extends for 28 km east of Rosetta Nile branch-estuary. The sands come out of the estuary are subjected to north-westerly winds and a current parallel to the beach line from west to east. The significant data about this heavy mineral distribution are shown in Fig. 1 and 2, and summerized in Tables 1–5. The Ilmenite properties especially the trace elements are also comprehended. Systematic withdrawal of 258 auger samples were distributed in a grid with 400 m parallel, and 200 m perpendicular to the beach line and 1 m depth. The main Ilmenite concentrations are present in three areas A, B and C. The Ilmenite content varies generally between 2. 2% as minimum and 18. 12% as maximum. The top meter (upper 1 m) contains 2. 91 million dry tons in an area covering 21 km². The Ilmenite forms the major mineral in the beach sands nearly north of Rosetta (Fig. 1 and 2). The principal richness of Ilmenite is contained in the area "B" which is close to Abu-Khashaba. The average value of Ilmenite all over the beach comes to 8. 128%. The mineral is found in normal distribution (Fig. 3) and this confirmed the deposition parallel to the beach line and irregular deposition perpendicular to the beach line. This is in accordance with the dominant current from the west to the east. The Magnetite is separated by using natural small magnet in one hand, as well as the Ilmenite, Hematite, Monazite, Zircon, Rutile and Garnet in the other hand by using the FRANTZ Isodynamic separator. The Ilmenite is estimated by using the separator in two different steps of suitable tilt and current.     

Gold in the beach placer sands of Chavakkad-Ponnani,Kerala Coast,India

Although sporadic mining of placer gold from river beds is not uncommon in India, there is no documented literature on the occurrence of gold in the beach placer sand deposits of the country. While characterizing the heavy minerals of the Chavakkad-Ponnani (CP) beach placer sands along the North Kerala coast, the association of gold with the pyriboles in these sands has been observed. A native gold grain of about 25 μm was seen to occur as an inclusion within an amphibole of hornblendic composition. The pyriboles of the CP deposit are angular to sub-angular indicating a nearby provenance that may be in the upstream reaches of the Ponnani River in the districts of Malappuram and Palakkad or further north in the auriferous tracts of the Wynad-Nilambur or Attapadi regions. It is argued that the occurrence of native gold in CP deposit is not a freak occurrence and that it warrants thorough investigation of all the pyribole-ilmenite-rich placers to examine the possible presence of gold and its abundance in the beach placers of northern Kerala coast.     

Radionuclides measurements and mineralogical studies on beach sands, East Rosetta Estuary, Egypt

Radiometric measurements were carried out for the beach sands from East Rosetta estuary to determine the activity concentrations of 238 U, 226 Ra, 232 Th, and 40 K, using a Hyper Pure Germanium spectrometer, to estimate the dose rates and radiation hazard indices. The average specific activities are 778.20 Bq/kg for 238 U; 646.89 Bq/kg for 226 Ra; 621.92 and 627.85 Bq/kg for the 222 Rn daughters 214 Pb and 214 Bi respectively. The average specific activity of 232 Th is 1510.25 Bq/kg, while the calculated specific activity for 40 K has an average of 8.41 Bq/kg. The average specific activity of 235 U is 38.61 Bq/kg. The average absorbed dose rate is 1211.36 nGy/h, 20 times higher than the estimated average global primordial radiation of 60 nGy/h and 6 times higher than that of the world range (10-200 nGy/h). The radium equivalent (Ra eq ) values are from 6 to 9 times the recommended value. The internal and external hazard indices (H int , H ex ) indicate that their values are from 6 to 11 times the permissible values of these indices. These higher values may be due to the presence of economic heavy minerals containing radionuclides as zircon and monazite as well as some trace minerals, thorite and uranothorite. The mineralogical study indicates the beach sands contain heavy minerals, zircon, monazite, rutile, ilmenite, leucoxene, magnetite and garnet. The average abundance of zircon is 0.175 wt% ranging from 0.125 wt% to 0.239 wt%, while it is 0.004wt% ranging from 0.001 wt% to 0.007 wt% for monazite. The average abundance is 0.087 wt% for rutile; 2.029 wt% for ilmenite; 1.084 wt% for magnetite; 0.384 wt% for leucoxene and 0.295 wt% for garnet.     

Natural and artificial radioactivity distribution in soil, rock and water of the Central Ashanti Gold Mine, Ghana

Direct gamma spectrometry study was carried out within and around the operational area of the Central Ashanti Gold of Ghana to ascertain the baseline radioactivity levels of naturally occurring radioactive materials (NORM), prior to processing of gold ore at the mine. The average activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in the soil/rock samples were 64.3, 68.4, 1243.9 and 3.5 Bqkg^?1, respectively. For the water samples, the average activity concentrations were 2.5, 2.6, 14.7 and 0.7 BqL^?1 for ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs, respectively. The total annual effective dose to the public was estimated to be 0.141 mSv which is below the ICRP recommended level of 1 mSv for public exposure control. The average radium equivalent activity value was 257.8 Bqkg^?1 in the range of 72.9–402.3 Bqkg^?1. The average values of external and internal indices were 0.7 and 0.8, respectively. The concentrations of U, Th and K were variable in soil and rock samples taken from different locations in the study area with values varying in the range of 0.8–10.9, 2.4–39.4 μg/g and 0.7–6.3 %, respectively. The concentration values of gross-α and gross-β for all the water samples were below the Ghana Standards Board and Who Health Organisation recommended guideline values for drinking water quality. The results obtained in this study shows that radiation levels are within the natural background radiation levels found in literature and compared well with similar studies for other countries.     

Some problems associated with the analysis and interpretation of mixed carbonate and quartz beach sands,illustrated by examples from North-West Ireland

Mixes of carbonate and quartz sands, which are commonly encountered in Recent coastal sediments, require careful analysis if they are to be correctly interpreted. Grain-size data fall into multimodal or segmented zig-zag distributions which may require some kind of component separation if they are to be summarised by conventional statistics, and before they can be assigned to a particular hydrodynamic depositional process or environment. Unfortunately, separation techniques are only spasmodically applied, usually without due regard to the consequences. Such artificially filtered or truncated distributions are of little subsequent use. Using a range of samples from two beaches in NW Ireland, where carbonate proportions range from nearly zero to over sixty percent, the interrelationships of the two dominant components were examined. Where only a small carbonate proportion is incorporated into a large quartz one, predictable modifications of the size-curve are apparent. However, the components are more independent if mixtures are near equal. The occurrence of a number of distinctive combinations of simple straight lines and complex zig-zag curves probably reflects the relatively dynamic nature of the carbonate fraction.     

Multigroup discrimination of river, beach, and dune sands using axial-ratio sample statistics of quartz grains

Optimal discrimination among several groups can be achieved by simultaneous diagonalization of pooled within-group, W, and among-group, A, sums of squares and cross-product matrices formed by utilizing axial-ratio sample statistics of quartz grains belonging to different sieve grades. This method maximizes the ratio of among-group cross products to within-group cross product quadratic forms (V'AV/V'WV)and simultaneously yields discriminant scores whose correlation coefficients are zero for group means as well as for within each group. This procedure enables a simple Euclidean distance measure for partitioning the discriminant space for assignment. Although W^–1 and Amatrices are symmetric, the W^–1 Amatrix needed for multigroup discrimination is asymmetric and hence the eigenstructure of W^–1 Ais obtained by simultaneous diagonalization of Wand Amatrices. The first four sample statistics (mean, standard deviation, skewness, kurtosis) of normalized axial-ratios are required for discrimination, although the mean and standard deviation are the most important discriminators.     

Natural radioactivity in sediment of Wei River,China

The concentrations of natural radionuclides in sediment of Wei River of China were measured using γ-ray spectrometry with the aim of estimating the radiation hazard as establishing a database for radioactivity levels of river sediment of China. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in sediment samples ranged from 10.4 to 39.9 Bq kg⁻¹, 15.3 to 54.8 Bq kg⁻¹ and 514.8 to 1,175.5 Bq kg⁻¹, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities of Chinese soil and Shaanxi soil. Radium equivalent activity (Ra_eq), external hazard index (H _ex) and representative level index (I _γr) were calculated for the samples to assess the radiation hazards arising due to the use of these sediment samples in the construction of dwellings. All the sediment samples have Ra_eq lower than the limit of 370 Bq kg⁻¹, H _ex less than unity and I _γr close to 1 Bq kg⁻¹. The overall mean outdoor terrestrial gamma dose rate is 64.8 nGy h⁻¹ and the corresponding outdoor annual effective dose is 0.079 mSv. None of the studied location is considered a radiological risk and sediment can be safely used in construction.     

Morphodynamics of a mesotidal rocky beach: Palmeras beach,Gorgona Island National Natural Park,Colombia

The response of a rocky beach to different possible combinations of hydrodynamic conditions (tides, waves, oceanic currents) has been little studied. In this work, the morphodynamic response to different hydrodynamic forcing is evaluated from sedimentological and geomorphological analysis in seasonal and medium term (19 years) scale in Palmeras beach, located in the southwest of Gorgona Island National Natural Park (NNP), a mesotidal rocky island on the Colombian Pacific continental shelf. Palmeras is an important nesting area of two types of marine turtles, with no anthropogenic stress. In the last years, coastal erosion has reduced the beach width, restricting the safe areas for nesting and conservation of these species. Until now, the sinks, sources, reservoirs, rates, and paths of sediments were unknown, as well as their hydrodynamic forcing. The beach seasonal variability, from October 2010 to August 2012, was analyzed based on biweekly or monthly measurements of five beach profiles distributed every 200 m along the 1.2 km of beach length. The main paths for sediment transport were defined from the modeling of wave currents with the SMC model (Coastal Modeling System), as well as the oceanic currents, simulated for the dry and wet seasons of 2011 using the ELCOM model (Estuary and Lake COmputer Model). Extreme morphologic variations over a time span of 19 years were analyzed with the Hsu and Evans beach static equilibrium parabolic model, from one wave diffraction point which dominates the general beach plan shape. The beach lost 672 m³/m during the measuring period, and erosional processes were intensified during the wet season. The beach trends responded directly to a wave mean energy flux change, resulting in an increase of up to 14 m in the width northward and loss of sediments in the beach southward. This study showed that to obtain the integral morphodynamic behavior of a rocky beach it is necessary to combine information of hydrodynamic, sedimentology and geomorphology in different time scales.     

Discrimination of accreted and eroded coasts using heavy mineral compositions of the Nile Delta beach sands, Egypt

Coastal erosion has occurred on the beaches of the three major promontories of the Nile Delta of Egypt. The eroded sand is generally carried alongshore to the east, or locally to the west, from these promontories and is deposited in areas of beach accretion between promontories. In this study the heavy minerals of 150 samples have been investigated with the aim of differentiating between eroded and accreted beaches. Discrimination was achieved by using bivariate plots of the raw weight percentage data and Q-mode factor analysis. Factor analysis yielded two ‘mineral assemblages’: Factor 1 is dominated by augite, hornblende and epidote, while Factor 2 consists of opaque minerals, garnet, zircon, rutile and monazite. These two mineral factors are produced by the selective sorting of heavy minerals by natural processes of waves and currents. Minerals of Factor 2 are associated with high density opaques which tend to concentrate as a lag in areas of erosion. Conversely, the lower density minerals of Factor 1 are preferentially transported away from areas of erosion and carried to the accreted shorelines.